Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$166.83	3.663%	$172.941	$172.94	$172.95	$172.90
Purchase #2	$70.42	9.586%	$77.1705	$77.17	$77.15	$77.20
Purchase #3	$226.52	6.532%	$241.3163	$241.32	$241.30	$241.30
Purchase #4	$153.30	11.776%	$171.3526	$171.35	$171.35	$171.40
Purchase #5	$65.54	7.543%	$70.4837	$70.48	$70.50	$70.50
Purchase #6	$128.65	12.113%	$144.2334	$144.23	$144.25	$144.20
Purchase #7	$163.46	5.438%	$172.349	$172.35	$172.35	$172.30
7 purchase totals =	$974.72		$1,049.8465	$1,049.84	$1,049.85	$1,049.80